1. Field of the Invention
The present invention relates to a constant voltage source, a constant voltage source circuit board and a method for supplying a constant voltage. The present invention also relates to a Japanese Patent Application No. 2000-3970 filed at Jan. 12, 2000, which is incorporated herein by reference.
2. Description of the Related Art
There is a conventional method for testing a semiconductor integrated circuit device using a semiconductor testing apparatus, where a constant voltage is supplied to the semiconductor integrated circuit device and a constant-current is measured. The semiconductor testing apparatus includes a constant voltage source for applying a constant voltage to a load. However, when the load enters into an operating state from a stand-by state, a current flows out of the constant voltage source and the voltage in the constant voltage source near the semiconductor device drops.
In general, a conventional constant voltage source has an operational amplifier and a feedback circuit The feedback circuit provides output voltage feedback to the operational amplifier, so that voltage variation is suppressed. However, as the operating speed of the semiconductor integrated circuit increases, testing on a high frequency range is required. Therefore, the output voltage feedback by the feedback circuit cannot follow the voltage variation.
Another conventional constant voltage source includes a bypass capacitor near the load in order to suppress voltage drop in the constant voltage source near the load. Since the bypass capacitor is located near the load, it is possible to correct the output voltage quicker than the feedback circuit. Therefore, it is possible to perform testing on a high frequency range, which is required as the operating speed of the semiconductor integrated circuit increases.
However, since the bypass capacitor is located near the load, the area of the bypass capacitor should be small. Therefore, it is impossible to make the capacitance of the bypass capacitor be enough to fully correct the output voltage variations. Further, in general, the bypass capacitor is coupled to the load in parallel. Therefore, a resistor and the constant voltage source in the constant voltage source form a CR circuit. The frequency characteristics of the CR circuit and the operational amplifier make the operation of the constant voltage source on a high frequency range unstable. If the capacitance of the bypass capacitor is increased, the operation of the constant voltage source becomes unstable even on a low frequency range.
Recently, operating speed of the semiconductor device has become increasingly faster. Therefore, it is required that the semiconductor testing apparatus perform a stable operation on a high frequency range by considering line resistances etc. as the operating speed increases. Further, it is also desirable to increase operating speed of the testing apparatus in order to increase throughput.
Therefore, it is required that the constant voltage source supply a predetermined level of output voltage to the load independently of the variation of currents supplied to the load.
Further, it is also required that the constant voltage source fully correct the output voltage supplied to the load before output voltage feedback of the feedback circuit follows the output voltage variation if the output voltage variation is dependent on the variation of currents flowing to the load.
Further, it is also required that the constant voltage source supply stable output voltage to the load during the operation on a high frequency range as the operating speed of a semiconductor integrated circuit device increases.
Further, it is also required that the semiconductor testing apparatus perform a stable testing on a high frequency range by considering line resistances etc. as the operating speed of a semiconductor integrated circuit device increases, and that the operating speed of the testing apparatus be increased in order to increase throughput.
Therefore, it is the object of the present invention to provide a constant voltage source, a constant voltage source circuit board and a method for supplying a constant voltage, which can meet the above and other requirements. The above object of the present invention can be achieved by combinations of features of independent claims. Dependent claims provide other preferred features of the present invention.
Therefore, it is an object of the present invention to provide a constant voltage Source, a constant voltage source circuit board and a method for applying a constant voltage which is capable of overcoming the above drawbacks accompanying the conventional art. The above and other objects can be achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the present invention.
According to the first aspect of the present invention, a constant voltage source circuit comprising: a constant voltage supplying circuit comprising an operational amplifier for supplying an output voltage to a load and a feedback circuit for feeding back the output voltage to the operational amplifier; a first inductance unit disposed between the constant voltage supplying circuit and the load; and a first bypass capacitor of which one terminal is coupled between the first inductance unit and the load and the other terminal is coupled to a constant voltage unit.
Inductance between the first bypass capacitor and the load of the constant voltage source circuit may be smaller than inductance between the constant voltage supplying circuit and the load.
The constant voltage source circuit may further comprise a first resistor coupled to the first inductance unit in parallel.
The constant voltage source circuit may further comprise a compensation circuit comprising a second resistor, a second inductance unit and a second bypass capacitor, one end of each of the second resistor, the second inductance unit and the second bypass capacitor being coupled to each other, wherein the other end of the second resistor is coupled to an end of the first inductance unit near the constant voltage supplying circuit, the other end of the second inductance unit is coupled to a load side end of the first inductance unit and the other end of the second bypass capacitor is coupled to the constant voltage unit.
Inductance between the second bypass capacitor and the load of the constant voltage source circuit maybe larger than inductance between the first bypass capacitor and the load.
Capacitance of the second bypass capacitor of the constant voltage source circuit may be larger than capacitance of the first bypass capacitor.
Inductance of the second inductance unit of the constant voltage source circuit maybe smaller than inductance of the first inductance unit.
At least one of inductances between respective the first and second bypass capacitors and the load of the constant voltage source circuit maybe inductance of respective wiring lines between the first and second bypass capacitors and the load.
At least one of the first and second inductance units of the constant voltage source circuit may be a wiring line.
Inductances between respective the first and second bypass capacitors and the load of the constant voltage source circuit may be inductances of wiring lines between the first or second bypass capacitors and the load, and the first and second inductance units may be wiring lines.
The constant voltage source circuit may further comprise: a first compensation circuit comprising a second resistor, a second inductance unit and a second bypass capacitor, one end of each of the second resistor, the second inductance unit and the second bypass capacitor being coupled to each other, wherein the other end of the second resistor is coupled to an end of the first inductance unit near the constant voltage supplying circuit, the other end of the second inductance unit is coupled to a load side end of the first inductance unit and the other end of the second bypass capacitor is coupled to the constant voltage unit; and a second compensation circuit comprising a third resistor, a third inductance unit and a third bypass capacitor, one end of each of the third resistor, the third inductance unit and the third bypass capacitor being coupled to each other, wherein the other end of the third resistor is coupled to an end of the first inductance unit near the constant voltage supplying circuit, the other end of the third inductance unit is coupled to a load side end of the first inductance unit and the other end of the third bypass capacitor is coupled to the constant voltage unit.
Inductance between the second bypass capacitor and the load of the constant voltage source circuit may be larger than inductance between the first bypass capacitor and the load, and inductance between the third bypass capacitor and the load may be larger than inductance between the second bypass capacitor and the load.
Capacitance of the second capacitor of the constant voltage source circuit maybe larger than capacitance of the first capacitor, and capacitance of the third capacitor may be larger than capacitance of the second capacitor.
Inductances of the second and third inductance units of the constant voltage source circuit may be smaller than inductance of the first inductance unit, and inductance of the third inductance unit may be larger than inductance of the second inductance unit.
Resistance of the third resistor of the constant voltage source circuit maybe larger than resistance of the second resistor.
At least one of inductances between respective the first, second and third bypass capacitors and the load of the constant voltage source circuit may be inductance of respective wiring lines between the first, second and third bypass capacitors and the load.
At least one of the first, second and third inductance units of the constant voltage source circuit may be a wiring line.
Inductances between respective the first, second and third bypass capacitors and the load of the constant voltage source circuit may be inductances of respective wiring lines between the first, second and third bypass capacitors and the load, and the first, second and third inductance units may be wiring lines.
According to the second aspect of the present invention, a constant voltage source circuit board comprises: a constant voltage supplying circuit comprising an operational amplifier for supplying an output voltage to a load and a feedback circuit for feeding back the output voltage to the operational amplifier; a first inductance unit disposed between the constant voltage supplying circuit and the load; and a first bypass capacitor of which one terminal is coupled between the first inductance unit and the load and the other terminal is coupled to a constant voltage unit, wherein the first bypass capacitor is disposed near the load.
The first inductance unit of constant voltage source circuit board may be a wiring line.
The constant voltage source circuit board may further comprise: a first compensation circuit comprising a second resistor, a second inductance unit and a second bypass capacitor, one end of each of the second resistor, the second inductance unit and the second bypass capacitor being coupled to each other, wherein the other end of the second resistor is coupled to an end of the first inductance unit near the constant voltage supplying circuit, the other end of the second inductance unit is coupled to a load side end of the first inductance unit and the other end of the second bypass capacitor is coupled to the constant voltage unit; and the second bypass capacitor is disposed at a place farther than a place where the first bypass capacitor is disposed from the load.
At least one of inductances between respective the first and second bypass capacitors and the load may be inductance of respective wiring lines between the first and second bypass capacitors and the load.
At least one of the first and second inductance units may be a wiring line.
Inductances between respective the first and second bypass capacitors and the load maybe respectively inductances of wiring lines between the first and second bypass capacitors and the load, and the first and second inductance units may be wiring lines.
Capacitance of the second capacitor may be larger than capacitance of the first capacitor.
Inductance of the second inductance unit may be smaller than inductance of the first inductance unit.
The constant voltage source circuit board may further comprise: a second compensation circuit comprising a third resistor, a third inductance unit and a third bypass capacitor, one end of each of the third resistor, the third inductance unit and the third bypass capacitor being coupled to each other, wherein the other end of the third resistor is coupled to an end of the first inductance unit near the constant voltage supplying circuit, the other end of the third inductance unit is coupled to a load side end of the first inductance unit and the other end of the third bypass capacitor is coupled to the constant voltage unit, and the third bypass capacitor is disposed at a place farther than a place where the second bypass capacitor is disposed from the load.
At least one of inductances between respective the first, second and third bypass capacitors and the load may be inductance of respective wiring lines between the first, second and third bypass capacitors and the load.
At least one of the first, second and third inductance units may be a wiring line.
Inductance between respective the first, second or third bypass capacitors and the load may be inductance of respective wiring lines between the first, second or third bypass capacitors and the load, and the first, second or third inductance units may be wiring lines, respectively.
Capacitance of the second capacitor may be larger than capacitance of the first capacitor, and capacitance of the third capacitor may be larger than capacitance of the second capacitor.
Inductance of the third inductance unit may be larger than inductance of the second inductance unit and smaller than inductance of the first inductance unit.
At least one of the first, second and third bypass capacitors may be disposed around the load.
At least a portion of the wiring line may be disposed around the load.
At least a portion of at least one of wiring lines between respective the first, second and third bypass capacitors and the load may be piled over other wiring line.
One wiring line of constant voltage source circuit board may be insulated from the other wiring line.
At least a portion of at least one of wiring lines between respective the first, second and third bypass capacitors and the load may be formed to pile up over at least one of the first, second and third bypass capacitors.
One wiring line of constant voltage source circuit board may be coupled to an electrode of the at least one of the first, second and third bypass capacitors.
At least a portion of at least one of wiring lines between respective of the first, second and third bypass capacitors and the load may be formed to pile up over the load.
According to the third aspect of the present invention, a method for supplying a predetermined voltage to a load comprising steps of: generating a voltage by using a constant voltage supplying circuit comprising an operational amplifier for generating the voltage supplied to the load and a feedback circuit for feeding back the output voltage from the operational amplifier to the operational amplifier; supplying the voltage to the load through a first inductance unit disposed between the constant voltage supplying circuit and the load; supplying a current to the load by using a first bypass capacitor of which one terminal is coupled between the first inductance unit and the load and the other terminal is coupled to a constant voltage unit; and charging the first bypass capacitor through the first inductance unit.
The summary of the invention does not necessarily describe all necessary features of the present invention. The present invention may also be a sub-combination of the features described above. The above and other features and advantages of the present invention will become more apparent from the following description of the embodiments taken in conjunction with the accompanying drawings.